The present invention relates to a bifunctional phenylene ether oligomer compound having a thermosetting functional group at each terminal, an epoxy resin containing the above oligomer compound and a use thereof. More specifically, it relates to a sealing epoxy resin composition for sealing an electric part, an epoxy resin composition for laminates, a laminate, a printed wiring board, a curable resin composition and a photosensitive resin composition. The resins and resin compositions of the present invention are used in electronics fields in which a low dielectric constant, a low dielectric loss tangent and high toughness are required and also used for various uses such as coating, bonding and molding.
As for materials for use in an electric or electronic field, as the speed of transmission signal increases, a low dielectric constant which decreases a time delay and a low dielectric loss tangent which decreases a loss are desired for utilizing a high-frequency wave (gigahertz band). Further, higher toughness is also desired in order to inhibit the occurrence of microcracks which are thought to be generated by thermal shock and secure high reliability. For the above demands, there are carried out attempts of incorporation of engineering plastic, such as polyphenylene ether (PPE), as a modified polymer having several properties. However, since a thermoplastic resin is directly incorporated into a thermosetting resin, problems remain with regard to the compatibility between the resins and molding processability.
For improving the compatibility, a method of improving compatibility by blending PPE with a different resin as a compatibilizing agent is discussed and the pseudo IPN structuralization of PPE and a cyanate resin is also discussed (JP-A-11-21452, etc.). However, the problems of molding processability and heat resistance have not been solved yet. Further, a method of converting a high molecular PPE into a low molecular compound is discussed for improving moldability. For example, there is known a method in which a high molecular PPE and polyphenols are redistributed in the presence of a radical catalyst (JP-A-9-291148, etc.). Further, for obtaining toughness, there is known a method in which a bivalent phenol and a monovalent phenol are subjected to oxidation polymerization to obtain a thermosetting resin having a cyanate ester group (JP-B-8-011747).
Concerning a semiconductor device, an epoxy resin composition is generally used for sealing electronic parts such as a semiconductor. The above-mentioned epoxy resin composition is composed of various epoxy resins such as a cresol novolak type epoxy resin, a bisphenol A type epoxy resin and a biphenyl type epoxy resin, a curing agent therefor, an inorganic filler, a curing accelerator as required, a coupling agent, a releasing agent, a coloring agent and the like.
In compliance with recent requirements for a decrease in size or a decrease in thickness, the formation technique of the above electronic parts is being changed from a conventional through hole mounting method (DIP: dual inline package, etc.) to a surface mounting method (SOP: small outline package, QFP: quad flat package, etc.). In the surface mounting method, since a semiconductor device is treated at a high temperature (for example 210xc2x0 C.xcx9c260xc2x0 C.) at a solder reflow or the like at a mounting time, a high temperature heat is applied to the entire semiconductor device. In this case, problems such as the occurrence of cracks in a sealing layer formed of the above epoxy resin composition and a large decrease in humidity resistance are apt to occur.
Countermeasures against the above are proposed. One countermeasure with respect to handling is that a semiconductor device before mounting is packaged in a moisture-proof case. As an improvement in a sealing epoxy resin composition, for example, JP-A-1-108256 discloses a sealing material containing a biphenyl type epoxy resin and JP-A-64-24825 discloses a sealing material containing an epoxy resin and a polyphenylene ether type resin in combination.
However, these sealing materials have problems. For example, when a thin sealing layer having a thickness of 2.0 mm or less is used, cracks are apt to occur at the time of a solder reflow. In view of a further improvement in physical properties and an increase in a signal transmission speed in a chip circuit, it is demanded to carry out a sealing with a sealing layer having a lower dielectric constant.
With the advance of communication or computers, recently, higher frequency waves come to be used. Printed wiring boards are required to have low dielectric characteristics for the purpose of increasing a signal transmittal speed. For responding to the above demands, there are used thermoplastic resins such as a fluororesin excellent in dielectric characteristics or a general polyphenylene ether. However, these thermoplastic resins have problems about workability, moldability, heat resistance and the like. For example, the problems are that a solvent used for preparing a varnish is limited, and that due to a high melt viscosity, a high multilayer formation can not be carried out and a high temperature and a high pressure are required at a molding time
On the other hand, as a thermosetting resin, there are known a polyphenylene ether modified epoxy resin, a thermosetting type polyphenylene ether and the like. However, conventional thermosetting resins have the same problems as the above problems of the thermoplastic resins. Further, a cyanate ester resin is known as a thermosetting resin having excellent dielectric characteristic and excellent moldability. However, when a cyanate ester resin alone is used, a cured product is too hard and is fragile so that it has a problem about adhesive property and solder resistance. When a cyanate ester resin is used in combination with an epoxy resin, the above defects can be covered. However, it is difficult to cope with requirements of lower dielectric characteristics of laminates, which requirements are becoming severer, by using a conventional cyanate ester resin in combination with a conventional epoxy resin.
Epoxy (meth)acrylate compounds have been widely used as raw materials for various functional high molecular materials such as a photosensitive material, an optical material, a dental material, an electronic material and crosslinking agents for various polymers. However, since higher performances are required in these application fields in recent years, physical properties required as a functional high molecular material become severer increasingly. As such physical properties, for example, heat resistance, weather resistance, low moisture absorptivity, high refractive index, high fracture toughness, low dielectric constant and low dielectric loss tangent are required. Until now, these required physical properties have not been necessarily satisfied.
For example, concerning the production of a printed wiring board, it is known that epoxy (meth)acrylate compounds are used for a photo solder resist used as a permanent mask. As a resist material like above, there are known a novolak type epoxy acrylate compound disclosed in JP-A-61-243869, a bisphenol fluorene type epoxy acrylate compound disclosed in JP-A-3-205417 and acid-modified products of these epoxy acrylate compounds. In a use for a printed wiring board, heat resistance in an immersion into a solder bath is demanded. When the heat resistance is insufficient, swelling or peeling off of a resist film occurs, which causes defectives.
In addition to the above-mentioned heat resistance, recently, as the speed of transmission signal becomes high, a lower dielectric constant which decreases a time delay and a lower dielectric loss tangent which decreases a loss are desired for utilizing a high-frequency wave (gigahertz band) However, a conventional epoxy (meth)acrylate compound is insufficient in dielectric characteristics for coping with a high-frequency wave. For this reason, a novel epoxy (meth)acrylate compound which satisfies the above requirements is demanded.
It is an object of the present invention to provide a thermosetting resin having the excellent electric characteristics and toughness of polyphenylene ether (to be referred to as xe2x80x9cPPExe2x80x9d hereinafter) and improved in compatibility with a different resin and molding processability.
It is another object of the present invention to provide molded articles which can be widely used in various uses including a use in an electronics field.
It is further another object of the present invention to provide a sealing epoxy resin composition capable of giving a sealing layer which is free from the occurrence of cracks when it is exposed to a high temperature, such as a temperature in a solder reflow, and has a low dielectric constant.
It is further another object of the present invention to provide a thermosetting resin composition excellent in dielectric characteristics and also excellent in moldability, heat resistance and the like, a laminate using the thermosetting resin composition and a printed wiring board.
It is further another object of the present invention to provide a novel (meth)acrylate compound and a curable resin composition which have excellent heat resistance and have a low dielectric constant and a low dielectric loss tangent.
According to the present invention 1, there is provided a thermosetting resin represented by the formula (1), 
wherein xe2x80x94(Oxe2x80x94Xxe2x80x94O)xe2x80x94 is represented by the formula (2) in which R1, R2R7 and R8 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, R3, R4, R5 and R6 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group and A is a linear, branched or cyclic hydrocarbon having 20 or less carbon atoms or an aromatic group, xe2x80x94(Yxe2x80x94O)xe2x80x94 is represented by the formula (3) in which R9 and R10 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group and R11 and R12 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, xe2x80x94(Yxe2x80x94O)xe2x80x94 is an arrangement of one kind of structure defined by the formula (3) or a random arrangement of two or more kinds of structures defined by the formula (3), Z is an organic group which has one or more carbon atoms and may contain an oxygen atom, each of a and b is 0 or an integer of 1 to 300, provided that at least either a or b is not 0, and each of i is independently 0 or an integer of 1.
According to the present invention 2, there is provided a sealing epoxy resin composition containing as ingredients an epoxy resin, a curing agent, an inorganic filler and a polyphenylene ether oligomer compound having a number average molecular weight of 700 to 3,000 and having an epoxy group at each terminal, represented by the formula (9), 
wherein xe2x80x94(Oxe2x80x94Xxe2x80x94Oxe2x80x94)xe2x80x94, xe2x80x94(Yxe2x80x94O)xe2x80x94, Z, A and i are as defined in the formula (1), each of a and b is 0 or an integer of 1 to 20, provided that at least either a or b is not 0, each of c and d is 0 or an integer of 1 to 20, provided that at least either c or d is not 0, and j is 0 or an integer of 1 to 5.
According to the present invention 3, there are provided an epoxy resin composition for laminates, containing a polyphenylene ether oligomer epoxy compound having a number average molecular weight of 700 to 3,000 and having an epoxy group at each terminal, represented by the above formula (9), and a curing agent as ingredients, prepreg and a printed wiring board.
According to the present invention 4, there are provided a (meth)acrylate compound represented by the following formula (10), a curable resin composition containing the (meth)acrylate compound and a cured product obtained by curing the curable resin composition, 
wherein R1 is a hydrogen atom or a methyl group, xe2x80x94(Oxe2x80x94Xxe2x80x94O)xe2x80x94 is represented by the formula (11) in which R2, R3, R8 and R9 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, R4, R5, R6 and R7 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group and A is a linear, branched or cyclic hydrocarbon having 20 or less carbon atoms, xe2x80x94(Yxe2x80x94O)xe2x80x94 is an arrangement of one kind of structure defined by the formula (12) or a random arrangement of two or more kinds of structures defined by the formula (12) in which R10 and R11 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group and R12 and R13 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, Z is an organic group which has no OH group in a side chain and has one or more carbon atoms and which may contain an oxygen atom, each of a and b is 0 or an integer of 1 to 300, provided that at least either a or b is not 0, and each of c and d is 0 or an integer of 1.
According to the present invention 5, there are provided an epoxy (meth)acrylate compound represented by the formula (16), a curable resin composition containing the above compound and a cured product of the above resin composition, 
wherein R1, xe2x80x94(Oxe2x80x94Xxe2x80x94O)xe2x80x94, A, xe2x80x94(Yxe2x80x94O)xe2x80x94, a, b, c and d are as defined in the formula (10), Z is an organic group which has one or more carbon atoms and may contain an oxygen atom, and n is 0 or an integer of 1 to 10.
According to the present invention 5, further, there is provided an epoxy (meth)acrylate compound according to the above, wherein R2, R3, R8 and R9 in xe2x80x94(Oxe2x80x94Xxe2x80x94O)xe2x80x94 are a methyl group, and xe2x80x94(Yxe2x80x94O)xe2x80x94 has an arrangement structure of the formula (4) or the formula (5) or a random arrangement structure of the formula (4) and the formula (5).
According to the present invention 6, there is provided a thermosetting resin represented by the formula (17), a resin composition for laminates containing the above thermosetting resin, prepreg obtained by using the resin composition and a printed wiring board, 
wherein xe2x80x94Xxe2x80x94 is represented by the formula (18) in which R1, R2, R7 and R8 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, R3, R4, R5 and R6 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group and A is a cyclic hydrocarbon or an organic group having an aromatic group, xe2x80x94(Oxe2x80x94Y)xe2x80x94 is represented by the formula (19) in which R1 and R10 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group and R11 and R12 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, xe2x80x94(Oxe2x80x94Y)xe2x80x94 is an arrangement of one kind of structure defined by the formula (19) or a random arrangement of two or more kinds of structures defined by the formula (19), Z is an organic group which has one or more carbon atoms and may contain an oxygen atom, each of a and b is an integer of 0 to 300, provided that at least either a or b is not 0, and each of i is independently an integer of 0 or 1).